diff --git a/Lib/fontTools/ttLib/macUtils.py b/Lib/fontTools/ttLib/macUtils.py
index cf4867277..8a92e669d 100644
--- a/Lib/fontTools/ttLib/macUtils.py
+++ b/Lib/fontTools/ttLib/macUtils.py
@@ -59,7 +59,7 @@ class ProgressBar:
 		self.bar.label(text)
 	
 	def close(self):
-		self.bar.d.HideWindow()
+		self.bar.d = None
 		del self.bar